Magnetic disks such as hard disks, and magnetic disk devices are widely used as external memories for computers.
Referring to FIGS. 15 and 16, the following description will explain a conventional magnetic recording and reproducing device for recording and reproducing information using the magnetic disk.
As illustrated in FIG. 15, the conventional magnetic recording and reproducing device records and reproduces information on a recording layer 122b (FIG. 16) of a magnetic disk 122.
The magnetic recording and reproducing device feeds an input signal from a host system 171 to an encoder 175 through an interface 172, a system controller 173, and an ECC (error correcting codes) circuit 174. After encoding the input signal into a serial magnetic-field-modulated signal by the encoder 175 and amplifying the signal by a pre-amplifier 176, the resultant signal is recorded as a magnetic pattern on the recording layer 122b of the magnetic disk 122 by a recording-use magnetic head 102 (FIG. 16) of a magnetic recording and reproducing head 150.
Meanwhile, a magnetic flux leaking from the recording layer 122b of the magnetic disk 122 according to a magnetization state is detected by a reproduction-use head 103 (FIG. 16), amplified by a pre-amplifier 180, adjusted in its waveform by a waveform equalizer 179, goes through a PLL (phase locked loop) circuit 178, and is decoded by a decoder 177. The decoded signal is output to the host system 171 through the ECC circuit 174, system controller 173, and interface 172, thereby reproducing information.
The serial signal amplified by the pre-amplifier 180 is also input to a servo circuit 181. By performing a feedback-control in response to the serial signal by a driver 182, tracking of the magnetic recording and reproducing head 150 with respect to the magnetic disk 122 is controlled. Moreover, the serial signal is also input to a servo circuit 183, to feedback-control the rotation speed of a spindle motor 184.
FIG. 16 shows the magnetic recording and reproducing head 150 used in the conventional magnetic recording and reproducing device. In the magnetic recording and reproducing head 150, the recording-use magnetic head 102 made of an inductive thin-film head and the reproduction-use head 103 made of a MR (magneto-resistive) head are mounted on the back surface of a floating slider 101. The floating slider 101 is supported by a suspension arm 120, and moves in a floated state over the surface of the magnetic disk 122 with a rotation of the magnetic disk 122 in a direction shown by arrow X6. Provided on the back surface of the floating slider 101 are head terminal electrodes 105 of the recording-use magnetic head 102, and head terminal electrodes 106 of the reproduction-use magnetic head 103. Lead wires 121 connected to the head terminal electrodes 105 and 106 are arranged along the suspension arm 120 and connected to electric circuits corresponding to the respective heads of the magnetic recording and reproducing device.
In general, for the recording layer of the magnetic disk, a material that is a hard magnetic material and also a ferromagnetic material, for example, CoPtCr, is used.
The magnetic disk 122 is fabricated, for example, by forming a 0.5-.mu.m-thick recording layer 122b made from a ferromagnetic material such as CoPtCr on a 1.5-mm-thick disk substrate 122a.
When recording information, a current corresponding to the information to be recorded flows in the recording-use magnetic head 102 through the head terminal electrodes 105 of the recording-use magnetic head 102. At this time, recording is carried out by sequentially inverting the magnetization of the recording layer 122b of the magnetic disk 122 by a signal magnetic field formed by a leakage magnetic flux from the head gap of the recording-use magnetic head 102. The arrows in FIG. 16 represent the magnetization state.
When reproducing information, the magnetic flux leaking from the recording layer 122b according to the magnetization state of the recording layer 122b of the magnetic disk 122 is detected by the reproduction-use head 103. Then, a signal is output from the head terminal electrodes 106 of the reproduction-use magnetic head 103, thereby reproducing the information.
The track width Lt of the magnetic disk 122 on which information is recorded in the above-mentioned manner is determined by the width of the recording-use magnetic head 102. Therefore, if the width of the reproduction-use magnetic head 103 is made narrower than the track width Lt, the reproduction output is lowered. On the other hand, if the width of the reproduction-use magnetic head 103 is made wider than the track width Lt, information from an adjacent track is mixed (i.e., crosstalk occurs). Thus, the recording-use magnetic head 102 and reproduction-use magnetic head 103 are usually fabricated to have substantially the same width.
Meanwhile, an increase in quantity of information to be processed has created a demand for high recording density. In order to achieve high-density recording, it is necessary to improve not only the linear density of recording bits, but also the track density (i.e., reduce the track width Lt). Hence, efforts to reduce the track width of the magnetic heads have been made.
In order to realize high-density recording by using a magnetic recording and reproducing head of the above-mentioned conventional structure to improve the track density, it is essential to reduce the widths of the recording-use magnetic head and reproduction-use magnetic head.
However, a reduction in the track width by a decrease in the width of the reproduction-use MR (magneto-resistive) head increases the hysteresis of the magnetic properties of the head, causes readout errors, and shortens the life of the head. A reduction in the track width by a decrease in the width of the recording-use head causes a lowering of leakage signal magnetic field from the gap, resulting in insufficient recording. Furthermore, since the track width is decreased, it is necessary to fabricate the heads with high precision.